The scary part is that we're still dealing with conventional mass shootings, which law enforcement is struggling to respond to, politicians can't agree on the proper laws to effectively deal with the issue, and intelligence agencies are trying desperately to track and preemptively stop these attacks from happening. We're not really dealing with technical mass killings just yet, and to be honest they have the potential to make the Vegas killing look like child's play. Imagine a series of drones hovering above equipped with guns or worse yet, IEDs dropped into crowds and the persons controlling the drones can be miles away. Here is a small drone that a group of teenagers built that can remotely fore a pistol. Very scary ****.
Imagine police, politicians, and intelligence trying to deal with is type of threat.
http://youtu.be/MBBC-xL_MTg
The military actually has a drone they bought from a contractor(can't recall who) that intercepts and fires a net that envelopes the hostile drone and makes it crash.
They are test deploying it at several Air Force bases to deal with kids and others flying their drones into bases and interfering with take offs.